Switching frames of the type here envisaged may be used to establish semipermanent connections between a number of incoming lines and a like number of outgoing lines of a central office; the term "lines", as here used, includes both local circuits and signal paths leading to remote stations. In some instances, as with a private branch exchange (PBX) or switchboard, the number of outgoing lines may differ from the number of incoming lines.
In all these cases it is necessary for an operator to have ready access to line terminations, such as jacks or plugs, between which a connection is to be made or broken; such access is also desirable for the purpose of connecting testing equipment to an incoming or outgoing line.
Conventional modular units of this description, which must be bolted to one another and to a supporting frame member, are inconvenient to readjust since their accessibility is limited and the process of disassembling and reassembling is time-consuming.